The present invention relates to the field of continuously treating textile threads, whether they be constituted by a plurality of continuous filaments or by discontinuous filaments of natural, synthetic, or artificial origin.
A method of continuous treatment, in particular dyeing, is known in particular from documents FR.2.098.428 and FR.2.122.708 in which wet thread that has passed through an impregnation chamber is caused to pass through a zone having a flow of air traveling therealong at a pressure which is much lower than the pressure that existed around the thread during the operation that caused it to be wetted. The low pressure zone is created in the supersonic flow of air at the outlet from a converging-diverging nozzle through which the thread passes. An improvement of that method is described in documents FR.2.219.268 and FR.2.250.421 and consists in imparting turbulence to the flow of air without rotating the thread.
According to the Applicant, that action of drying the thread by air is far from satisfactory in avoiding splashes from the treatment bath, in particular a bath of dye, on the thread leaving the apparatus and prior to being dried. In addition, when the method is put into operation, it is not easy to thread the thread through the various impregnation and drying members, and it is necessary to make use of hooks which are in the form of fine wire rods.
Document FR.2.282.492 discloses a method of continuous treatment intended mainly for treating a fiber tape by means of a false-twist member for the purpose of untwisting the tape after it has received injection of a liquid, which may be a colored liquid. In that method, at the outlet from the false-twist member, the fiber tape is surrounded by a liquid sheath which, in the preferred application, enables fibers to be bonded to the tape by adhesion.
An object of the present invention is to make it possible to treat all kinds of thread, whether constituted by fibers or continuous filaments, while avoiding uncontrolled splashing of the treatment bath, and guaranteeing that the thread is easy to put into place when starting the method.
This object is completely achieved by the method of treating thread in continuous displacement which, in characteristic manner, comprises the following successive operations, taken in the thread displacement direction:
a) a suction operation in which the thread is sucked through an air suction nozzle;
b) a spraying operation in which a treatment bath is sprayed onto the thread by means of at least one spray nozzle;
c) a removal operation in which the air and the treatment bath that has not been taken up by the thread are removed;
d) a false-twist operation in which an air false-twist member twists the thread; and
e) optionally an operation of drying the thread; the spraying operation being capable of being performed either upstream or downstream from the suction operation.
In this method, and contrary to the teaching of document FR.2.098.482, there is no complete impregnation of the thread by passing through a treatment bath. Instead said treatment bath is sprayed, with the spraying being performed preferably at high pressure to force the treatment bath to penetrate into the core of the thread in displacement. The quantity of bath that is sprayed is adjusted as a function of the desired take-up rate, with the air of the suction nozzle removing surplus treatment bath. Naturally, the primary function of the air suction nozzle is to apply traction on the thread in its displacement direction, said traction making it possible, when the method is set into operation, to thread the thread without it being necessary to use mechanical means. The spraying operation while the thread is being inserted on starting the method is preferably not itself started until after the thread has been threaded.
Advantageously, the bath is a bath of dye and contains a resin including pigments. In which case, it is possible to obtain a dyed thread after the drying operation alone and without any need for steaming or thermosetting.
Another object of the invention is to provide an apparatus specially designed for implementing operations a) to d) of the above-specified method. The apparatus comprises in succession, and on the path of the thread: an air suction nozzle; at least one spray nozzle for spraying a treatment bath; a removal chamber for removing the air and the excess treatment bath; and an air false-twist member.
Another object of the invention is to propose an installation for treating thread continuously, the installation comprising, on the path of the thread and in its displacement direction: first delivery means; the above-specified apparatus; second delivery means; drying, thermosetting or steaming means, and receiver means.
The drying means preferably consist in two heating drums with offset axes, the thread being wound over said drums and moving in the form of substantially touching turns.